Jian-Ming Chang

An energy-efficient geographic routing protocol design in vehicular ad-hoc network

The combination of vehicles and wireless communication has resulted in a promising future for vehicular ad hoc networks (VANETs). The VANET is a kind of network that can be built randomly, quickly and temporarily without any infrastructure. The routing of data in a VANET is a challenging task due to the high dynamics, unstable connection environments and transfer direction limit (real road planning) involved. However, it has been discussed that radio obstacles, as found in urban areas, have a significant negative impact on the performance of location based routing. Therefore, the design of a suitable routing protocol for VANETs is an important issue, especially in regard to inter-vehicle communication applications. This paper proposes a energy-efficient geographic routing algorithm that uses the direction, density and distance between nodes in the crossroad routing strategy, to improve the link stability. We compare the novel scheme, ad hoc on-demand distance vector, and dynamic source routing (DSR) for packet loss rate and average end-to-end delay in VANETs to reduce the power consumptions. The simulation results are obtained which demonstrate the power effectiveness of our proposed routing strategy.

An Efficient Service Discovery System for Dual-Stack Cloud File Service

Cloud services have attracted much attention in recent years as networking systems for the information connection devices of organizations or enterprises around the world have become increasingly sophisticated. Cloud services also provide a variety of services for users, including virtual hosting services, storage services, and Web application services. Distributed computing and the peer-to-peer (P2P) network are two important elements in cloud computing. However, the huge numbers of information devices currently in use present some new problems, such as the lack of IPv4 protocol addresses. Therefore, the IPv6 protocol was proposed. During the transition period from pure IPv4 to pure IPv6, IPv4 and IPv6 will coexist on the Internet. To link independent dual-stack P2P networks around the world, we herein propose a mechanism to improve the service discovery in dual-stack cloud file service, thus decreasing the amount of protocol translation and improving the efficiency of the bandwidth and load balance. From the simulation results, we conclude that the proposed mechanism can achieve higher connection success rate, efficient bandwidth, and a lower connection build time. Our paper indicates that the connection success rate and efficient bandwidth outperforms the other schemes by approximately 20% and 24%, respectively.

Mobile Relay Stations Navigation-Based Self-Optimization Handover Mechanism in WiMAX Networks

Organic Computing has similar characteristics of organism whose can be self-adjustment for a variety of conditions. The goal of Organic Computing is to develop a computing system which meets people demands and operates automatically in the information network. WiMAX (Worldwide Interoperability for Microwave Access) provide high-speed access and a coverage range several kilometers, but actual coverage range was few kilometers only due to the shelter of buildings or terrain. IEEE 802.16 working group designed 802.16j-based RS (Relay Station) to overcome above problem. In this paper, we present a mechanism called Self-Optimization Handover Mechanism which uses GPS (Global Positioning System) navigation system to combine with mobility characteristics of Mobile Relay Station, especially, the concept of Self-Optimization of Organic Computing integrated into this mechanism. An ASN-establishment of a database server is the most important hope that through this database to store information related to GPS navigation, and through this server to calculate the base station handover. By using our proposed mechanism, a base station can be planned in advance on the path of choice. To reduce the number of possible handover, scanning the channels and by the waste channel scanning the time it takes, hoping to provide a more stable WiMAX services. KeywordsWiMAX; 802.16j; handover; Mobile Relay Station; GPS navigation

Design of Dead-End-Avoidance Method for Geographic Forwarding in MANET

Geographic forwarding is part of geographic routing in that each node only needs to know the location of its neighbors and the destination. This method can reduce the cost of table-driven routing which needs to maintain the whole path, even if the path is not in use. It also saves time when searching the path, as compared with reactive routing. When using geographic forwarding, it usually happens that the local maximum cannot forward the packet directly to the destination; this fundamental problem is called Dead End. We use the A star (A*) algorithm, which is usually used in role-playing or strategic games, to detour around terrain that cannot be passed through directly. Nodes must vote on an agent in a specific area to be a decision-maker and find a reference route for the source node. When the route is decided, geographic forwarding is used according to this reference path to the destination to avoid the dead end.

Optimized path selection mechanism for IEEE 802.16j Multi-Hop Relay networks

When the mobile station (MS) is far away from the base station (BS) or terrain and buildings interfere with transmission, the data rate decreases with the increased distance from the BS, and the coverage range of the BS will be shortened to only a few kilometers. The IEEE Working Group has proposed the 802.16j relay technology. This technology can be used to forward data for a BS while overcoming the signal strength attenuation. Since the cost of constructing the relay station is low, the MS will have to scan more than one signal when entering the Mobile Multi-Hop Relay (MMR) network. In this paper, we introduce a novel path selection mechanism that exploits the remaining slot and signal strength indicator (SSI). Since the signal strength will affect the Modulation and Coding Scheme (MCS) combination, we propose to use SSI integrated with the MCS, taking the hop count into account. We demonstrate that our proposed scheme is capable of producing an optimal path selection.

MR-Chord: A scheme for enhancing Chord lookup accuracy and performance in mobile P2P network

In the recent years, Peer-to-Peer (P2P) sharing network has become very popular in the Internet. However, most P2P protocols are designed for traditional wired networks. When deployed in wireless network environment, many challenges are encountered. For instance, the nodes in an unstable wireless network tend to leave or rejoin the P2P network easily. In this case, the routing information in every node must become overdue, which may lead to lookup failures when the nodes retrieve these overdue routing information. In this paper, we propose a modified Chord protocol called MobileRobust-Chord (MR-Chord). MR-Chord is designed with the aim of keeping the Finger Table fresh. To achieve this goal, we have modified the Distributed Hash Table (DHT)-based protocol a Chord Protocol in such a way that the Finger Table is kept updated to provide the necessary lookup services in the P2P network. Simulations studies show that our proposed MR-Chord protocol outperforms the original Chord protocol in the following aspects: (1) increase in the lookup success rate and overlay consistency, (2) reduction of the lookup delay time.

An Energy-Efficient Dynamic Duty-Cycle and Dynamic Schedule Assignment Scheme for WSNs

Wireless Sensor Network (WSN) is still a hottest research topic which can be applied to a lot of new research field such as robotic and smart grid. Its not only used for detecting the new environment but also monitoring any situation which has dynamic variation. However, the sensor node is relied on the battery energy that limited the lifetime of entire network. In this paper, we proposed a novel scheme called Dynamic Duty cycle and Dynamic Schedule Assignment (DDDSA) which not only can reduce number of RTS/CTS (Request to Send / Clear to Send) packets but also dynamically update the Duty Cycle value. Furthermore, the proposed scheme does not calculate the traffic information repeatedly in overlapping areas. This scheme will reduce more idle nodes to achieve energy efficiency.

PIMac: Multicast Access Control Implementation in PIM-SM

In this paper, we present an access control scheme for PIM-SM multicast domain. In order to avoid the overhead of digital signature algorithm, the proposed solution makes use of the Rendezvous Point to collect keys and implement a distributed shared-key based multicast access control system. As it supplies efficient host access control in PIM-SM domain, we name this scheme PIMac. Compared with the existing multicast admission control solutions, PIMac has following advantages: (1) support both receiver and sender access control; (2) realize host exclusion based on expire time; (3) compatibility with current PIM-SM protocol; (4) lower join latency; (5) anti-replay and DoS robustness; last but not least, (6) PIMac architecture is divided into two separated domains: AAA domain and multicast routing domain, entities in each domain do not rely on PKI interoperability or common secret to authenticate each other. The experimental results show that PIMac achieves flexible manageability and improves the performance of multicast access control systems effectively.

Using a novel efficient location management approach in cellular networks

When a mobile terminal enters a new location area (LA), it always updates its current location information to its home location register(HLR), when a call arrives, the system will page the mobile terminal (MT) based on its most recent updating. If location update (LU)frequency increases, the update cost increases. Decreasing location update would make the paging cost increases. In this paper, we propose an intelligent approach, it is an integrated location management scheme that combines rule base paging scheme (RBPS)and traveling salesman mobility (TSM) model scheme. It applies an intelligent paging scheme with movement based LU strategy to resolve the total cost which is comprised of paging cost and LU cost. Also, it attempts to resolve the issue of inherent tradeoff between the paging cost and LU cost in location management. Analytical results show that proposed integrated new scheme, it does reduce the total cost for location management compared to the previous scheme, and obtain the better performance.

Design a Novel Scheme for Dual-Stack Cloud File Service Discovery Based on Distributed Hash Table

Cloud services attract some attention in recent years, the information connection devices of organizations or enterprises with one another distributed around the world using networking systems. Cloud services also provide variety services for users, including virtual hosting services, storage services and web application services, etc. Because of the rise of cloud computing, users can directly enjoy the benefits of distributed computing. The high throughput of computing power and large storage space can be ubiquitous when users connect to the Internet. Two important elements behind clouds computing include distributed computing and peer-to-peer network. However, the huge numbers of information devices today bring forth some new problems. The lack of IPv4 protocol addresses is one of the serious problems. Therefore, the IPv6 protocol was proposed, and during the transitional period form pure IPv4 to pure IPv6, IPv4 and IPv6 will coexist in the Internet. To link independent dual-stack p2p networks around the world, we hereby propose a mechanism to improve the service discovery in dual-stack cloud file service in hope of decreasing the count of protocol translation so as to improve the efficiency of the bandwidth and load balance.